Studia Geologica Polonica  vol. 104 (Abstracts)

Geology of Cretaceous rocks at Paradise Harbour, Danco Coast, Antarctic Peninsula

Krzysztof BIRKENMAJER

Abstract
The area of Paradise Harbour, Danco Coast, is part of the Mesozoic magmatic arc of Antarctic Peninsula. It consists of: (1) Early Cretaceous basaltic lava-agglomerate pile (Antarctic Peninsula Volcanic Group, APVG) some 2000 m thick, with subordinate rhyodacite lava intercalations, formed in a marginal marine basin setting, post-dated by (2) Cretaceous Andean plutons (Andean Intrusive Suite, AIS-1: granite, granodiorite, diorite, gabbro), and (3) Cretaceous acidic, intermediate and basic hypabyssal dykes (AIS-2). The APVG effusives rest unconformably upon sedimentary basement formed by strongly folded Trinity Peninsula Group (TPG: Paradise Harbour Formation, Permo-Triassic ?). The APVG, together with its TPG basement and, possibly, also a part of Andean plutons (AIS-1) and younger dykes (AIS-2) are involved in SE-vergent, retro-arc thrusts. The thrust-folding could be an expression of the oceanic Aluk Ridge/Antarctic Peninsula magmatic Arc collision in a   sector between the Tula and Anvers Fracture Zones during the Tertiary.

Studia Geologica Polonica, 104: 41-104.

Lithostratigraphy and tectonics of the Miers Bluff Formation at Hurd Peninsula, Livingston Island (West Antarctica)

Marek DOKTOR, Anna ŚWIERCZEWSKA & Antoni K. TOKARSKI

Abstract
The Miers Bluff Formation (MBF) (redefined) is more than 1600 m thisc (base unknown). It is subdivided into three mappable members: the South Bay Member (SBM), more han 850 m thick (base unknown); the Johnsons Dock Member (JDM) about 150 m thick; and the Glaciar Rocoso member (GRM) aboy 600 m thick. The MBF is a marine, clastic, turbidite succession corresponding to the proximal (SBM and GRM) and distal (JDM) parts of a submarine fan. Six facies associations were distiguished in the MBF. These facies associations occur in different proportions in particular members. The whole succession is devoid of body megafossils and microfossils, although marine trace fossils were found in every member.
The petrologic differentiation of the MBF is insignificant. Its source area consisted largely of metamorphic and volcanic rocks, however no traces of contemporaneous extrabasinal volcanism were found. The source area was possibly a dissected continental margin.
The large majority of the MBF strata occur in tectonically inverted position. The MBF was deformed during three succesive stages: (1) regional folding around N25 oriented axis; and (2) and (3) brittle deformation in strike-slip tectonic regime with the maximum stress axis horizontal and oriented respectively N90 (2) and N0 (3). Two systems of joints, minor faults, quartz veins and magmatic dykes were formed during stages (2) and (3).

Studia Geologica Polonica, 104: 105-116.

Multilamellar Bryozoan colonies from the Eocene La Meseta Formation of Seymour Island, Antarctica: a preliminary account

Andrzej GAŹDZICKI* & Urszula HARA**

Abstract
An assemblage of multilamellar, spheroidal cheilostome and cyclostome bryozoans has been found in the lower part of the Eocene La Meseta Formation near Cape Wiman on Seymour (Marambio) Island, Antarctic Peninsula. The cyclostomes form massive, hemispherical colonies which are assigned to the genera: Ceriopora Goldfuss 1827 and Tetrocycloecia Canu 1919. The cheilostomatous, anascan bryozoans are constructed as spheroidal, slightly oblate, multilamellar colonies (the cellepori-form A ectoproctaliths) composed of successive overgrowing layers. They are represented by the genera of the family Membraniporidae Busk 1854. The zoarial growth form of the investigated multilamellar bryozoan colonies may indicate that these free-lying forms settled on a firm or loose substrate in tidal and deltaic sedimentary environments of the La Meseta Formation. This is the first record of such bryozoan biofacies from Antarctica.